Aspects of the present invention relate to communications. Other aspects of the present invention relate to packet based communication.
Data exchange between independent network nodes is frequently accomplished via establishing a “session” to synchronize data transfer between the independent network nodes. For example, transmission control protocol/Internet protocol (TCP/IP) is a popular implementation of such a session method. Data transferred over such an established session is usually fragmented or segmented, prior to transmission on a communication media, into smaller encapsulated and formatted units. In the context of input and output controllers such as Ethernet Media Access Controllers (MACs), these encapsulated data units are called packets. Since packets are originally derived from data of some communication session, they are usually marked as “belonging” to a particular session and such marking is usually included in (or encapsulated in) the packets. For instance, in a TCP/IP session, network addresses and ports embedded in the packets are used to implement per-packet session identification.
When packets of the same session are received at a destination, they may be temporarily stored in a buffer on an I/O controller prior to being further transferred to a host system where the packets will be re-assembled or defragmented to re-create the original data. The host system at a destination may be a server that may provide network services to hundreds or even thousands of remote network nodes.
When a plurality of network nodes simultaneously access a common network resource, packets from a communication session may be shuffled with packets from hundreds of other different sessions. Due to this unpredictable data shuffling, a host system generally processes each received packet individually, including identifying a session from the received packet and accordingly identifying a corresponding session on the host system to which the received packet belongs. There is an overhead on the host system associated with such processing. In addition, when a data stream is transmitted continuously under a communication session, each received packet, upon arriving at the host, may need to be incorporated into the existing data stream that constitutes the same session. Using newly arrived packets to update an existing session is part of the re-assembly or defragmentation. This further increases the overhead on the host system. Furthermore, the overhead may increase drastically when there are a plurality of concurrent communication sessions. High overhead degrades a host system's performance.
When notified of the arrival of a packet, a host system processes the packet, determines the packet's underlying session, and updates an existing session to which the arrived packet belongs. Processing one packet at a time enables the host system to better handle a situation in which packets from different sessions are shuffled and arrive in a random manner. It does not, however, take advantage of the fact that packets are often sent in bursts (or so called packet troops or packet trains).
There have been efforts to utilize such burst transmission properties to improve performance. For example, packet classification techniques have been applied in routing technology that exploits the behavior of packet train to accelerate packet routing. Packet classification techniques have also been applied for other purposes such as quality of service, traffic metering, traffic shaping, and congestion management. Such applications may improve the packet transmission speed across networks. Unfortunately, they do not impact a host system's (at the destination of the transmitted packets) capability in re-assembling the received packets coming from a plurality of underlying communication sessions.
A gigabit Ethernet technology known as ‘jumbo frames’ attempted to improve the performance at a destination. It utilizes “jumbo frames” that increases the maximum packet size from 1518 bytes (the Ethernet standard size) to 9022 bytes. The goal is to reduce the data units transmitted over the communications media and subsequently a network node may consume fewer CPU resources (overhead) for the same amount of data-per-second processed when “jumbo frames” are used. However, data units that are merged to form a larger unit are not classified. As a consequence, at destination, a host system may still need to classify packets before they can be used to re-assemble the data of specific sessions. Due to that, the overhead used to correctly recover the original data streams may still remain high.